Clean corona gas ionization for static charge neutralization

Abstract

Clean corona gas ionization by separating contaminant byproducts from corona generated ions includes establishing a non-ionized gas stream having a pressure and flowing in a downstream direction, establishing a plasma region of ions and contaminant byproducts in which the pressure is sufficiently lower than the pressure of the non-ionized gas stream to prevent at least a substantial portion of the byproducts from migrating into the non-ionized gas stream, and applying an electric field to the plasma region sufficient to induce at least a substantial portion of the ions to migrate into the non-ionized gas stream.

1. A gas ionization apparatus for delivering a clean ionized gas stream to a charge neutralization target, the apparatus receiving at least one non-ionized gas stream having a pressure and an ionizing electrical potential sufficient to induce corona discharge, the apparatus comprising:
 at least one through-channel for receiving the non-ionized gas stream and for delivering the clean ionized gas stream to the target, wherein the through-channel is at least partially formed of a conductive material and comprises a means for superimposing an electric field in response to application of a non-ionizing electrical potential; and 
 at least one shell assembly comprising: 
 a shell having an orifice in gas communication with the through-channel such that a portion of the non-ionized gas stream may enter the shell; 
 at least one evacuation port that presents a gas pressure within the shell and in the vicinity of the orifice that is lower than the pressure of the non-ionized gas stream outside the shell and in the vicinity of the orifice; and 
 at least one ionizing electrode for producing ions and byproducts in response to application of the ionizing electrical potential, the ionizing electrode being disposed within the shell such that at least a substantial portion of the produced ions may migrate into the non-ionized gas stream to thereby form the clean ionized gas stream and such that the evacuation port gas pressure induces a portion of the non-ionized gas stream to flow into the shell orifice to thereby sweep at least a substantial portion of the byproducts into the evacuation port. 
 
     
     
       2. A gas ionization apparatus for delivering a clean ionized gas stream to a charge neutralization target, the apparatus receiving at least one non-ionized gas stream having a pressure and an ionizing electrical potential sufficient to induce corona discharge, the apparatus comprising:
 at least one through-channel for receiving the non-ionized gas stream and for delivering the clean ionized gas stream to the target; 
 at least one shell assembly comprising:
 a shell having an orifice in gas communication with the through-channel such that a portion of the non-ionized gas stream may enter the shell; 
 at least one evacuation port that presents a gas pressure within the shell and in the vicinity of the orifice that is lower than the pressure of the non-ionized gas stream outside the shell and in the vicinity of the orifice; and 
 at least one ionizing electrode for producing ions and byproducts in response to application of the ionizing electrical potential, the ionizing electrode being disposed within the shell such that at least a substantial portion of the produced ions may migrate into the non-ionized gas stream to thereby form the clean ionized gas stream and such that the evacuation port gas pressure induces a portion of the non-ionized gas stream to flow into the shell orifice to thereby sweep at least a substantial portion of the byproducts into the evacuation port; and 
 
 at least one eductor that is upstream from the shell, the eductor having a motive connection for receiving the non-ionized gas stream and an exhaust connection for passing the non-ionized gas stream downstream to the through-channel. 
 
     
     
       3. The gas ionization apparatus of  claim 2  wherein
 the eductor is at least partially in gas communication with the through-channel and the exhaust connection of the eductor faces the shell orifice; and 
 the apparatus further comprises a non-ionizing electrode for superimposing an electric field in response to application of a non-ionizing electrical potential, the electrode being positioned outside of the through-channel and upstream of the shell orifice. 
 
     
     
       4. The gas ionization apparatus of  claim 2  wherein the eductor is at least partially in gas communication with the through-channel and the shell orifice faces the exhaust connection of the eductor. 
     
     
       5. The gas ionization apparatus of  claim 2  wherein
 the ionizing electrical potential is a radio-frequency electrical potential at least equal to the corona threshold of the ionizing electrode whereby the ionizing electrode produces both positive and negative ions; 
 the eductor further comprises a suction connection in gas communication with the evacuation port to thereby present the gas pressure in the vicinity of the orifice that is less than the pressure of the non-ionized gas stream in the vicinity of the orifice; and 
 the apparatus further comprises a byproduct trap in gas communication with the evacuation port and the suction connection of the eductor. 
 
     
     
       6. A gas ionization apparatus for delivering a clean ionized gas stream to a charge neutralization target, the apparatus receiving at least one non-ionized gas stream having a pressure and an ionizing electrical potential sufficient to induce corona discharge, the apparatus comprising:
 at least one through-channel for receiving the non-ionized gas stream and for delivering the clean ionized gas stream to the target; and 
 at least one shell assembly comprising: 
 a shell having an orifice in gas communication with the through-channel such that a portion of the non-ionized gas stream may enter the shell; 
 at least one evacuation port that presents a gas pressure within the shell and in the vicinity of the orifice that is lower than the pressure of the non-ionized gas stream outside the shell and in the vicinity of the orifice; and 
 at least one ionizing electrode for producing ions and byproducts in response to application of the ionizing electrical potential, the ionizing electrode being disposed within the shell such that at least a substantial portion of the produced ions may migrate into the non-ionized gas stream to thereby form the clean ionized gas stream and such that the evacuation port gas pressure induces a portion of the non-ionized gas stream to flow into the shell orifice to thereby sweep at least a substantial portion of the byproducts into the evacuation port, wherein the ionizing electrode comprises a tapered emitter pin with a sharp point that produces a generally spherical plasma region during corona discharge of ions, the point facing the shell orifice and being recessed from the shell orifice by a distance that is substantially equal to or greater than the diameter of the plasma region; 
 wherein the shell orifice is generally circular and has a diameter; and 
 wherein the ratio of the shell orifice diameter and the recess distance is between about 0.5 and about 2.0. 
 
     
     
       7. A gas ionization apparatus for delivering a clean ionized gas stream to a charge neutralization target, the apparatus receiving at least one non-ionized gas stream having a pressure and an ionizing electrical potential sufficient to induce corona discharge, the apparatus comprising:
 first and second through-channels for receiving the non-ionized gas stream and for delivering the clean ionized gas stream to the target; and 
 at least one shell assembly comprising: 
 a shell having an orifice in gas communication with the through-channel such that a portion of the non-ionized gas stream may enter the shell; 
 at least one evacuation port that presents a gas pressure within the shell and in the vicinity of the orifice that is lower than the pressure of the non-ionized gas stream outside the shell and in the vicinity of the orifice; and 
 at least one ionizing electrode for producing ions and byproducts in response to application of the ionizing electrical potential, the ionizing electrode being at least one strand of wire disposed within the shell such that at least a substantial portion of the produced ions may migrate into the non-ionized gas stream to thereby form the clean ionized gas stream and such that the evacuation port gas pressure induces a portion of the non-ionized gas stream to flow into the shell orifice to thereby sweep at least a substantial portion of the byproducts into the evacuation port.